The Development and Application of DDPCR Technology on Quantification of Total Coliforms in Water

In this research, the detection method for absolute quantification of total coliforms was established based on Droplet Digital Polymerase Chain Reaction (DDPCR) technology using lacZ as the target gene for coliform group detection. The experimental conditions (e.g. primer and probe concentrations, annealing temperatures, etc) were well optimized. Besides, the linear range, precision and limit of quantification (LOQ) of this method were investigated and evaluated. The results illustrated that the optimal primer concentration was 0.2 μmol/L, whereas the optimal probe concentration was 0.5 μmol/L. The optimal annealing temperature was 56°C. The linear relationship between the total coliform genome DNA concentrations derived from DDPCR and DNA fluorometer was quite good (R2 = 0.999). The linear range was 3.95 ~ 7.80 × 104 copies/20 μL DDPCR reaction system. The LOQ for total coliforms was single copy per reaction system. Practical applications using real water samples collected from water supply system in Macao illustrated that this innovative method possessed high efficiencies and capabilities. This is probably the first research using DDPCR technology to absolutely qualify and quantify total coliforms and successfully applied it in Macao water supply system. The achievements from this research could provide with significant values for setting-up the emergency mechanism of water pollution in early stage.